1. Field of the Invention
The present invention relates to a printed circuit board with an improved heat dissipation efficiency. In particular, the present invention relates to a printed circuit board with an improved heat dissipation efficiency that has a ventilating hole for heat dissipation formed by separating a composite-molded board off the main printed circuit board.
2. Description of the Related Art
Printed circuit boards of electronic or electric apparatus, such as a television set and a video recording/reproducing device (a DVD recorder, for example), have various types of electronic components, electronic devices and the like mounted thereon. Many of these electronic components and the like generate considerable amounts of heat. In addition, many of them cannot operate stably at higher temperatures. Thus, the heat generated in the electronic apparatus has to be dissipated successfully. With the recent trends toward higher packaging densities for smaller or thinner products and toward higher powers for higher performance, such a thermal problem has become more important.
According to a conventional solution to such a problem, a ventilating hole is formed in the housing of the electric apparatus to release the heat generated in the apparatus to the outside. Furthermore, a ventilating hole is formed also in the printed circuit board in the apparatus to form air paths from the outside to the inside and vice versa, thereby enhancing the heat dissipation efficiency.
Prior art techniques concerning the printed circuit board with a ventilating hole for heat dissipation described above are disclosed in Japanese Utility Model Laid-Open Publication No. 5-55590 (Patent Document 1) and Japanese Patent Laid-Open Publication No. 2002-93928 (Patent Document 2).
According to some prior art techniques, successive cuts are formed in the printed circuit board, and a portion of the printed circuit board is separated off to form a hole in the board, thereby facilitating heat dissipation of an electronic component on the board. According to the prior art technique disclosed in Patent Document 1, such a heat-dissipating hole is formed by press working, thereby saving the cost of forming such a board portion to be separated off (a sacrificial board) and eliminating the need for the separation step. However, the prior art technique disclosed in Patent Document 1 requires an additional press die and an additional press working step.
On the other hand, the electric apparatus often requires a plurality of boards, such as “a main board responsible for the processing of the whole apparatus and a sub board responsible for a specific processing”. Therefore, conventionally, in order to improve the board efficiency and enable processing of a plurality of boards in one step, composite molding is conducted (to be specific, the main board and the sub board are formed as a dividable one board, treated as one board when conducting a processing common to the boards, and then separated from each other for use as the separate boards).